Field of the Invention
The drawing of FIG. 14 shows a cross-sectional view of the conventional 4-pole synchronous motor disclosed in the unexamined Japanese patent publication HEI 9-191618. The drawing of FIG. 15 shows a vertical section of the conventional synchronous motor of FIG. 14. The drawing of FIG. 16 shows a cross-sectional view of the rotor of the conventional synchronous motor of FIG. 14. Referring to the drawings, the reference numeral 1 denotes a rotor. The rotor 1 after laminating the steel in the axial direction, is fixed to the output shaft 3 by using the pressing method or by using the other likewise methods.
In addition to that, the reference numeral 9 denotes a stator. The stator 9 is formed by laminating the steel in the axial direction. In addition to that, the reference numeral 10 denotes windings wound around the stator 9. When an electric current is flown through the windings 10, then the electric current produces a rotating magnetic field. The reference numeral 12 denotes the plurality of slits radialy aligned so that the central part of the electric motor is protruding beyond. The slits 12 have air gaps inside them. Either that or the slits 12 are replenished with non-conductive, non-magnetic material inside them so as to magnetically isolate the plurality of magnetic circuits 13. Referring to FIG. 16, the reference numeral 14 denotes a thin connector unit. Various parts of the rotor 30 should not be completely disunited by the slits. As can be seen in detail at the Part B of FIG. 16, the slits 12 do not fully separate the outer periphery of the rotor 30. The strength of the rotor 30 is maintained by the adjustment of the thickness of the thin connector unit 14.
According to this kind of conventional electric motor, the position and direction of the magnetic circuit 13 on the rotor 30 determines the position and direction of the field magnetic flux that can exist in the rotor 30. When an exciting current flows through the windings 10 of the stator 9 so that the magneto motive force acts on the direction of the field magnetic pole of the rotor 30, then the field magnetic flux is produced in a direction of the field magnetic pole of the rotor 30, and the rotational force is applied to the rotor 30. Therefore, for the kind of electric motor illustrated in FIG. 14, the rotor 30 rotates by synchronizing to the rotating fields produced at the windings 10 of the stator 9, and by developing the reluctance torque.
Like above, the slits of the conventional rotor 30 is symmetrically arranged with respect to the q-axis. The q-axis is the direction where the magnetic flux is difficult to flow. Depending upon the position of a slit of the rotating rotor, the generated magnetic flux must jump over the slit. Because of this, the flow of magnetic flux becomes bad. There was a problem of the losses and the efficiency becomes worse.
In addition to that, typically, the rotor 30 of the conventional electric motor which is shown in FIG. 11 has 4 poles or more consisting of even number poles. For instance, when operating the 4-pole electric motor with commercial business power source supply of a constant frequency of 50 Hz or 60 Hz, its rotational speed is only increased from 1500 rpm to 1800 rpm (revolutions per minute). When equip this electric motor to the compressor and the like, then a decrease in its output causes a problem. Insufficient performance of the compressor is the problem.
As the methods of enlarging the ability of compressor are to increase the operational frequency in the drive circuit of the inverter and the like. Alternatively, there is a method of increasing the capacity of the compressor. In both cases there was a problem that the cost becomes high.
In addition to that, the conventional synchronous motor has not had the secondary conductor inside the slit. Because of this, self-starting of the conventional synchronous motor is not possible with commercial business power source supply, unlike the general induction electric motor. In order to start the synchronous motor, it must make a start by using the dedicated amplifier such as inverter. Henceforth, there was a problem that the expensive control unit becomes necessary.
In addition to that, the conventional electric motor had taken no consideration as regard to the proportion of the magnetic material to the non-magnetic material in the q-axis direction. Because of this, the conventional electric motor has been used under many occurrences of losses and when the efficiency has been bad.
According to present invention, it designates that the synchronous motor having a high efficiency is obtained as purpose. In addition to that, it designates that the synchronous motor attaining a high performance is obtained as purpose. In addition to that, it designates that the synchronous motor having a low manufacturing cost is obtained as purpose. In addition to that, it designates that the synchronous motor with a simple structure having a high reliability which can withstand the rotary motion at a full speed is obtained as purpose.